Electric heating apparatus



W. S. MOODY. ELECTRIC HEATING APPARATUS. APPLICATION FILED JAN. 3, 1922.

1,48 6,891 Patented Nov. 28, 1922.

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Patented Nov. 28, 1922.

UNITED STATES PATENT OFFICE.

WALTER S. MOODY, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY, A CORPORATION 01 NEW YORK.

ELECTRIC HEATING APPARATUS.

Application filed January 3, 1922.

7 '0 all whom it may concern:

Be it known that I, WALTER S. MOODY, a citizen of the United States, residing at Pittsfield, county of Berkshire, State of Massachusetts, have invented certain new and useful Improvements in Electric Heating Apparatus, of which the following is a specification.

My invention relates to electric heating 10 apparatus and has for its object the provision of an improved method of and means for heating elongated workpieces by means of low voltage alternating currents.

. More specifically my invention relates to the heating of workpieces of considerable length such, for example, as metallic pipes, by means of a heavy alternating current of low voltage which is passed through the workpiece so as to heat it by virtue of its own resistance. The usual method of heating articles in this manner is to connect the low voltage secondary terminals of a transformer directly to the ends of the article or to the extremities of that portion which it is desired to heat. In such case when the article is of considerable length, the circuit takes the form of a large loop, which loop has a high reactance. With the heavy current required, a reactance voltage 1s de- 80 veloped in the heating circuit which is large as compared with the voltage necessary to overcome the resistance drop in the circuit. This causes a very low power factor in heating circuits of this character, which is a very undesirable feature.

In carrying out my invention, I have arrangedthe heating circuit so as to eliminate nearly all of its reactance. This Ihave accomplished by arranging a portion of the heating circuit in close proximity along the length of the workpiece in such manner that the heating current passes through this portion in a direction opposite to its direction of flow in the workpiece. In this manner the reactances in the workpiece and the portion of the 'heating circuit in close proximity thereto are neutralized, or nearly so, by the current flowing in opposite directions therein, whereby the power factor of the circuit is increased.

For a more complete understanding of my invention, reference should be had to the accompanying drawing in which Fig. 1 is a View in section of heating apparatus for Serial No. 526,562.

modified form of my invention; while Fig.

3 is a sectional view of Fig. 2 along the line 3-3 looking in the direction of the arrows. Referring to Fig. 1 of the drawing, in one form of my invention the metallic pipe 10, which is to be heated, has inserted therethrough a tubular electrical conductor 11 made of a suitable material, such as copper. The conductor 11 is concentric with pipe 10 and extends the full length of the pi e, projecting from each end. On the rig hand projecting end of conductor 11 is fastened a flange member 12 of electrically conducting material. The flange member has a tapped central portion which engages suitable threads on the conductor, thus securing the flange member in electrically conducting relation with the conductor. An annular portion 13 having a tapered bore into which the end of ipe 10 extends is provided on flange 12. y means of a tapered split ring 14 which is wedged around pipe 10 between the pipe and the annular portion 13, the pipe is temporarily secured in electricall conducting relation with the flange 12. etachable clamping members 15 and 16, forming electric terminals, are secured to the lefthand ends of pipe 10 and conductor 11, re spectively. A suitable source of low voltage alternating current supply, shown as the low voltage secondary of a transformer 17, is connected to terminals 15 and 16.

As thus constructed and arranged, it will be observed that current will be supplied from transformer 17 to terminal 15, through pipe 10, flan e 12, conductor 11, and terminal 16, back to t e secondary of the transformer. The terminals, flange 12, and conductor 11 are of such low resistance that they will not be appreciably heated by the current, which is of low voltage and high amperage. The pipe 10, however, will beheated by reason of its own resistance by the passage of current. By means of this arrangement the heating current flows through the conductor 11 in a direction opposite to its flow inpipe 10. The reactances of the pipe and the conductor 11 are, therefore, neutralized, or nearly so, by the flow of currents simultaneously therethrough of equal strength and of opposite directions. In this manner the reactance of the heating circuit is reduced to a very low value, and the power factor correspondingly increased. Obviously, if desired, the conducting tube may be adapted to surround the trically conducting blocks 22 secured thereratus shown is only illustrative, and that the.

to, which are adapted to engage in electrically conducting relation with pipe 10 so as to complete an electric circuit from the pipe to the conducting tube. This construction provides a very convenient arrangement for applying and removing the conducting tube 11"since it is not necessary to insert the conductor into the'pipe, as shown in Fig. 1. By means of this arrangement sections of a pipe which is installed or otherwise immovable may be conveniently heated. Another advantage in having the conducting tube surround the heated pipe is that by lining the conducting tube with heat insulating material or by providing it with a dry heat reflecting interior surface, the conducting tube may be used to prevent loss of heat by radiation from the pipe.

In accordance with the provisions of the patent statutes, I have described the princi le of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the appainvention can be carried out by other means. What I claim as new and desire to secure I by Letters Patent of the United States, is,-

1. Electric heating apparatus comprising in combination with an elongated workpiece, of a source of low voltage alternating current supply, and electrical connections between said supply source and said workpiece forming a heating circuit therefor havmg a portion extending in close proximity to said workpiece in which the heating current flows in a direction opposite to its flow,

in the workpiece.

2'. Electric heating apparatus comprising in combination with an elongated workpiece, of a source of low voltage alternating current supply, and a conductor connecting said supply source to said workpiece extending along the length of said workpiece in close proximity thereto in which the heating current flows in a direction opposite to its flow in the workpiece.

3. Electric heating apparatus comprising in combination with an elongated workpiece, of a conductor detachably connected in electrically conducting relation to one end of said workpiece and extending along the length thereof in close proximity thereto, and a source of low voltage alternating current supply connected to said conductor and said workpiece for setting up a heating current flowing in opposite directions in said conductor and said workpiece.

4. Electric heating apparatus comprising in combination with an elongated workpiece, of a tubular conductor enclosing said workpiece and detachably connected in electrically conducting relation to one end there: of, and a source of low voltage alternating current supply connected to the free ends of said conductor and workpiece for setting up a heating current flowing in opposite directions in said conductor and workpiece.

5. The method of heating an elongated workpiece which consists in supplying low voltage alternating current to said workpiece through a conductor arranged in close proximity thereto so that the current flows in said conductor in a direction opposite to its flow in the workpiece.

6. The method of heating an elongated workpiece which consists in sup-plying low voltage alternating current to said workpiece througha conductor extending along the length of said workpiece in close proximity thereto and arranged so that the current fiows in said conductor in a direction opposite to its flow in the workpiece.

In witness whereof, I have hereunto set 

